Structure and Function of the Boundaries of Imprinted Genome Domains

哺乳动物的印记基因聚集在基因组的某些区域，形成“印记基因组结构域”。然而，目前还不清楚每个印迹域是如何定义或界定的。我们研究了7号染色体远端大印迹结构域的着丝粒边界（H19-L23 mrp基因间区）的结构和功能，并获得了以下结果。1 .一、在基因间区发现了一个无大ORF的非印迹转录本（Nctc 1）。2.人类和小鼠之间的序列比较揭示了10个进化上保守的片段，其中7个在转基因小鼠中作为组织特异性增强子。3.由于L23 mrp在体内不利用增强子，我们将L23 mrp转基因连接到增强子，并检查增强子是否可以在转基因小鼠中激活L23 mrp启动子。然而，启动子本身的活性太高而不能评估增强子对启动子的作用。4.非编码转录本的存在和增强子的成簇组织类似于珠蛋白基因座的基因座控制区（LCR）。由于已知球蛋白LCR含有边界元件或绝缘体，因此在该边界区域中可能存在类似的机制。

Imprinted genes of mammals are clustered at certain regions of the genome and forms "imprinted genome domains". However, it is unknown how each imprinted domain is defined or delimited. We investigated the structure and function of the centromeric boundary (H19-L23mrp intergenic region) of the large imprinted domain on distal chromosome 7, and obtained the following results. 1 . A non-imprinted transcripts with no large ORF (Nctc 1) was identified in the intergenic region. 2. A sequence comparison between human and mouse revealed ten evolutionarily conserved segments, and seven of these worked as tissue-specific enhancers in transgenic mice. 3. Since L23mrp does not utilize the enhancers in vivo, we linked an L23mrp transgene to the enhancers and examined whether the enhancers can activate the L23mrp promoter in transgenic mice. However, the activity of the promoter itself was too high to assess the effect of the enhancers on the promoter. 4. The presence of non-coding transcripts and the clustered organization of the enhancers resembled the locus control region (LCR) of the globin locus. Since the globin LCR is known to contain a boundary element or an insulator, it is possible that a similar mechanism operates in this boundary region.